This is a gem that checks the strength of a user-submitted password. It has a large number of downloads (37,000 on the legitimate 0.0.6 version). It looks like it's made to be integrated on webservers.
The modified gem downloaded and executed code stored in a editable Pastebin, meaning that the code could have changed at any time. Presumably, the malicious code would activate just by browsing any page on the affected site. One version of the Pastebin code would execute any code embedded in a magic cookie sent by a client. Plus, it would ping the attacker's server to let them know your webserver was infected.
The modified gem downloaded and executed code stored in a editable Pastebin, meaning that the code could have changed at any time. Presumably, the malicious code would activate just by browsing any page on the affected site. One version of the Pastebin code would execute any code embedded in a magic cookie sent by a client. Plus, it would ping the attacker's server to let them know your webserver was infected.
Nasty, nasty stuff.